Bridge strike at Penyffordd - confusing signage?

[Phil from Mon]

Our regional rag the Daily Post is reporting that the imperial and metric height limits on the bridge under which a lorry got stuck on Thursday, earning the driver a £100 fixed penalty, do not match. The imperial gives 13 feet, while the metric shows 4.1 metres, rather than the 3.96 it should be. Not much, but it could make all the difference between squeezing through and getting comprehensively wedged. Network Rail have declined to comment on the report.

 

[LWB]

Doesn't matter that they don't match so much as what is the actual height of the bridge. If there is 4.1m of clearance then signing it as 13ft in imperial is simply adding a safety margin. If there is only 13ft of clearance then there is an issue in signing it as 4.1m.

 

[Phil from Mon]

Doesn't matter that they don't match so much as what is the actual height of the bridge. If there is 4.1m of clearance then signing it as 13ft in imperial is simply adding a safety margin. If there is only 13ft of clearance then there is an issue in signing it as 4.1m.

Should have said the lorry is quoted as being 4m high

 

[LWB]

Should have said the lorry is quoted as being 4m high

So Network Rail need to get the tape measure out. If it reads 4.1m they're in the clear. Anything significantly less and ..... oops The 13ft is an irrelevance.

 

[Phil from Mon]

So Network Rail need to get the tape measure out. If it reads 4.1m they're in the clear. Anything significantly less and ..... oops The 13ft is an irrelevance.

Who has responsibility for the signage? Is it NR, or the local council, and if the latter do they do the measuring themselves or rely on what they're told by NR?

 

[158747]

Maybe the road has been resurfaced, reducing the clearance under the bridge.

 

[AndyPJG]

All to do with tolerances and rounding factors.

The signed height is worked out by measuring the actual minimum clearance, then deducting 3 inches and then rounding down to a multiple of 3 inches, so the displayed height will be between 3 to 5 inches less than the actual clearance. I can't recollect what the figures are for the metric equivalent are, but it is calculated in metric unitss and not converted from the displayed imperial value.

 

[LNW-GW Joint]

There has been another bridge strike on the Wrexham-Bidston line today, this time on the A550 at Caergwrle (the local rag says Cefn y Bedd half a mile away, but that doesn't seem right).
http://www.leaderlive.co.uk/news/14...er-skip-lorry-becomes-stuck-under-bridge.aspx
http://www.nationalrail.co.uk/service_disruptions/today.aspx

On the Penyffordd strike on the 18th, the offending truck is plainly Polish.
https://www.wrexham.com/news/trains-delayed-as-lorry-gets-stuck-under-penyffordd-bridge-95839.html

 

[kieron]

On the Penyffordd strike on the 18th, the offending truck is plainly Polish.
https://www.wrexham.com/news/trains-delayed-as-lorry-gets-stuck-under-penyffordd-bridge-95839.html

Whereas the latest one clearly isn't.

 

[LNW-GW Joint]

Whereas the latest one clearly isn't.

That firm is based locally - I hired a skip from them recently.
Can't plead unfamiliarity on that road!

 

[455driver]

When I worked for Yorkshire Traction they gave the drivers a bridge book which listed the location, marked height and actual clearance of all bridges on bus routes and diversions, sometimes there was quite a bit of difference between the two.

One that springs to mind was in Pontefract where it was marked up at 13ft8in but was only about 10ft6in (you could see it was nowhere near 13ft), when you consider that our deckers (Olympians and VRs) were marked at 13ft8in high it could lead to a bit of a problem!

 

[najaB]

One that springs to mind was in Pontefract where it was marked up at 13ft8in but was only about 10ft6in (you could see it was nowhere near 13ft)...

That's more than a rounding error! Though, it might lead to truncation instead.